1. Field of the Invention
This invention relates to methods for evaluating the aggregation of a proteinaceous material in a suspension comprising an organopolysiloxane and medical components having surfaces coated with organopolysiloxane(s) and containing suspensions of proteinaceous materials.
2. Description of Related Art
Therapeutic proteins provide numerous unique and critical treatments for diseases and conditions, such as diabetes, cancer, hemophilia, rheumatoid arthritis, multiple sclerosis and myocardial infarction. There are already dozens of protein products on the market and hundreds more are in preclinical and clinical development. Furthermore, with the recent advent of robust methods for “humanizing” antibodies, there has been a new resurgence in biotechnology product development due to the tremendous increase in the number of antibody products being investigated for treatments of human disease. With modem genomic and proteomic approaches, new, safer and more effective protein therapeutics are being discovered daily. However, if a protein product cannot be stabilized adequately, its benefit to human health will never be realized. The shelf life required for economic viability of a typical protein pharmaceutical product is 18-24 months. Achieving this goal is particularly difficult because of the relatively low thermodynamic stability of the protein in its native state. The activity of a protein depends on its native, three-dimensional structure. In addition, proteins are highly susceptible to the formation of non-native aggregates and precipitates, even under conditions that thermodynamically greatly favor the native state over the unfolded state (e.g., neutral pH at 37° C.). The biological activity of a protein in an aggregate is usually greatly reduced. More importantly, non-native protein aggregates can cause adverse reactions in patients, such as immune response or anaphylactic shock. The capacity of aggregates of a given protein to induce adverse responses cannot be predicted; nor can the maximal level of aggregates required for safety be determined without costly and time-consuming clinical trials.
Thus, a major goal of formulation science is to design a formulation in which aggregation is kept to an extremely low level. Generally, the goal is to have no more than 1-2% of the entire protein population form aggregates over the shelf life of the product. Even under solution conditions where protein physical stability appears to be optimized so as to minimize protein aggregation in the bulk solution, there can be formation of visible and subvisible protein particles that may constitute only a minute fraction of the total protein population. The presence of even a small number of protein particles can render a product clinically unacceptable. Protein particulates are particularly immunogenic. Although particulates are desirable for vaccine formulations (where protein molecules are bound to aluminum salt particles), in a therapeutic protein product, the immune response to such particles can cause severe adverse responses in patients. Thus, even though the mass of protein that aggregates can be so small as to have essentially no deleterious effect on product potency, safety can be greatly compromised.
Particle formation can occur routinely during processing steps such as pumping of protein solution during vial/syringe filling. In other cases, particle formation may appear to be random. For example, particles may be seen in a small fraction of vials or prefilled syringes in a given product lot. Other times, a product filled into a given lot of vials or syringes may form protein particles in a large fraction of the containers. Unfortunately, these particles appear downstream of sterile filtration steps and cannot be removed by filtration during subcutaneous, intradermal, or intramuscular injection.
Silicone oils are commonly used as lubricants in medical articles. While silicone oils are not subject to oxidation, migration and stick could occur for pre-filled syringes, and high breakout and/or breakloose forces are a problem. Silicone oil has been shown under certain conditions, even at low concentrations, to induce protein aggregation. Several newly commercialized aqueous protein products, including erythropoietins (e.g., Recormon™ and Eprex™), interferons (e.g., Avonex™ and Rebif™) and rheumatoid arthritis therapies (e.g., Enbrel™ and Humira™) are manufactured in prefilled syringes. Inner surfaces of prefilled syringes are coated with silicone oil to enhance syringe functionality, and consequently, formulated protein is exposed to silicone oil surfaces. Silicone oil induced therapeutic protein aggregation is a concern in the pharmaceutical industry, potentially leading to loss of product and increased manufacturing costs.
There is a need for methods to assess aqueous suspensions or emulsions having proteinaceous materials to determine appropriate aggregation inhibitors to include in the solution to inhibit aggregation. The results of these investigations will provide the understanding needed for advising companies on how to develop protein formulations that are resistant to silicone oil-induced protein aggregation. In addition, an experimental system that allows rapid formulation screening is desirable. Thus, pharmaceutical and biotechnology companies can follow a rational formulation development plan to quickly optimal formulations for each protein that avoid the problem of silicone oil-induced protein aggregation and the potential adverse responses in patients. Model proteins and appropriate solution conditions can be determined that can be used for testing new syringes or medical articles in development.